Method of making hypodermic syringes



March 6, 1956 J. v. MAGASH ET AL METHOD OF MAKING HYPODERMIC SYRINGES Filed April 16, 1951 MK mm H MMMM E R V6 m W5 T WWW MMD m w w v v United States Patent METHGD OF MAKING HYPGDERMIC SYRINGES Julius V. Magash, Waliington, and Charles Messineo, Lyndhurst, N. 3., assignors to Beaten Dickinson and Company, Rutherford, N. 1., a corporation of New This invention relates to a structurally and functionally improved hypodermic syringe assembly as well as the individual units of such an assembly.

Among objects of the present invention are those of providing a readily sterilized glass assembly in which no objectionable leakages or back-flows will occur and in which, moreover, the physician or other user will be able to easily observe a solution within the barrel; the assembly also having a long, useful life.

A further object is that of teaching a method of producing a syringe assembly and by means of which a grouping of parts may be provided at relatively low cost; the method being capable of being readily practised by workmen possessing ordinary skill.

With these and other objects in mind, reference is had to the attached sheet of drawings illustrating one practical embodiment of the invention and in which:

1 shows a complete assembly constructed in accordance with the present teachings;

Fig. 2 is a transverse sectional view taken along the line 22 and in the direction of the arrows as indicated in Pig. 1;

Fig. 3 is a longitudinal sectional view taken along the line 3-3 and in the direction of the arrows as also indicated in Fig. 1;

Fig. 4 is a fragmentary sectional view in enlarged scale of the preform utilized to provide the assembly;

Fig. 5 shows this unit after it has been subjected to a forming action;

Fig. 6 is a fragmentary sectional view similar to Fig. 5 but showing a plunger disposed in the bore of the barrel in order that the surface of that bore incorporate the desired finished characteristics; and

Fig. 7 is a fragmentary sectional view in further enlarged scale showing a detail of the parts as illustrated in Fig. 6.

As is well understood in connection with the production of glass hypodermic syringe assemblies, it has been customary to form pistons and barrels from suitable stock. Such forming has involved subjecting sections of stock to heating and shaping operations such that a plunger or piston unit has been provided in addition to a barrel which has ordinarily been formed with an outwardly extending manipulating flange at one of its ends and with the other end left open. The piston unit has then been subjected to a grinding operation involving a rough grind and one or more finishing grinds. The resulting piston has thus presented a circular face which is true insofar as it is possible to produce such a surface according to existing techniques and the skill of trained operators.

With respect to the barrel portion of the assembly it has been customary to use glass tubing and to subdivide the same into sections of proper length. As afore brought out it has also been usual to form adjacent one end of each these sections, a flange portion. The bore of the tube has been ground. In such grinding a number of steps Hce have been involved preferably including the use of abrasive material of increasing fineness. The barrel has been cleaned and its end thereupon provided with a conventional needle mounting portion.

According to procedure as heretofore practiced, a plunger of a size proper for inclusion as part of an operative hypodermic assembly has been selected. It was subjected to a number of reducing steps, the main purpose of which was that of presenting a plunger which would be capable of projection into and other movements with respect to the barrel bore. Such movements will occur in the presence of a fine abrasive. The latter assured a proper fit between the plunger and barrel. This fit has heretofore been characterized by a sealing surface on the plunger, which surface has a limited area and extends from a point spaced rearwardly from the outer plunger end to a point usually short of the center of that piston. This surface might be only one-fifth or less of the overall piston length. In advance and to the rear of the bearing surface or sealing zone the diameter reduction of the plunger was, in certain instances, as much as .001".

With suitable cleaning an assembly resulted which, according to accepted practice, included a matched barrel and piston. Both the outer surface of the latter and the face of the bore presented a satiny, finely ground, translucent surface. Graduation marks were applied to the outer face of the barrel to indicate, for example, cubic centimeters of volume and fractions of such cubic centimeters. Also, for purposes of identification, similar serial numbers have usually been applied to both the barrel and piston, having in mind that these units were now matched to each other and not capable of being freely interchanged with other units to produce a satisfactory assembly.

As is well understood, a hypodermic syringe is usually cleaned with detergents after each use. An assembly produced according to the afore-described technique has had limited life because of the small area providing the sealing surface and the attacking of that surface by the cleaning solution. When the sealing surface was sufliciently reduced it becomes inefiective to prevent leakage. Thereupon the syringe had to be replaced.

As will finally be understood with reference to the process as heretofore outlined and practiced, annealing steps and the detailed technique involved in applying graduations and other indicia to the parts has either not been described in detail, or else not even referred to, in that such procedure is well understood by those skilled in the art and is not necessary to an understanding of the present invention.

According to the present invention pistons or plungers may be formed and subjected to the action of a centerless grinder in order to embody a truly circular configuration. The grinding operation may involve any desired or necessary number of steps. Thereafter, the piston is lapped. Consequently a unit results which has a true diameter throughout its entire effective length beginning at a point adjacent its outer or barrel-entering end and extending through to a point adjacent its rear or actuating portion. Otherwise stated a sealing surface exists throughout substantially this entire zone and embraces a constant diameter. This surface has a lapped or satiny finish. Plungers or pistons produced in this manner are now grouped according to their diameters.

The barrels for use with the plungers are produced from preforms. To so produce these units a technique and structure is resorted to as is, for example, disclosed in the application for United States Letters Patent in the name of Henry G. Molinari and Julius V. Magash, Serial Number 337,525 on Forming Method and Machine filed February 18, 1953. The preform may embrace a tubular body having one end open and defined by a flange.

Its opposite end is conveniently closed and presents a needle supporting portion or tip. Such closing includes an end wall formed with an opening extending into the supporting portion. After the shrinking into contact with the surfaces of the mandrel and conforming to the contour of the latter as taught in such application, it is found that discrete particles forming part of the preform mass are brought to the bore surface of the barrel and project inwardly of the face of the same. These particles are minute and may embrace unmelted or unmerged grains of the material providing the glass compositions. They extend beyond the chill surface of the bore to a minute extent. As will be understood, that surface is the one which exists on all glass articles where a face is not subjected to grinding and lapping operations which break through and destroy the relatively hard surface and expose the underlying material providing the body of the glass article.

At this time or after a barrel thus formed is removed from the mandrel, it has its closed end incorporating the usual passage. 150, its tip or needle-supporting portion may have embraced in it suitable needle-mounting surfaces. Thereupon, it is conveniently subjected to an annealing action and a number of the barrels are grouped according to their bore diameter. After this operation has been completed they may receive indicia such as graduations, numbers, marks of origin, etc. etc. If, now, an attempt is made to reciprocate a plunger or piston of a proper size group within the bore of a barrel thus produced, unsatisfactory results will follow. These results will include uneven operation of the piston plus a tendency of the latter to jam within the barrel bore. In fact, in many instances, if these attempts are persisted in, actual jamming or freezing of the parts will occur. If a plunger is withdrawn from a barrel after having cooperated with the latter in the manner aforedescribed, small scratch marks are apparent. These indicate that the inwardly extending discrete particles projecting from the barrel body have engaged the surface of the piston and have, in certain instances, been severed so that they move in abrasive contact between the bore and piston surfaces and tend to wedge or lock the parts against movement.

In order to overcome difficulties in this connection a barrel is selected from a given bore diameter group and a plunger is selected from a corresponding diameter group. That plunger will have a minutely smaller diameter than the barrel bore. A small amount of very fine abrasive is applied, for example, throughout the entire length of the plunger. In certain instances it may be desired to merely apply the abrasive substance adjacent the outer or barrel-entering end of the plunger. In any event, the plunger is introduced into the barrel bore and relative movements are resorted to between the barrel and piston such that the parts receive a lapped fit. With the introduction of the plunger into the barrel and relative movements occurring in the presence of a suitably fine abrasive it is found that the particles extending inwardly from the surface of the bore are severed adja cent their base portions and the particles are reduced to an extent such that they present no problem. in the event that the surface defining the face portion of a severed particle is flush with and not below the bore surface then the relatively minute area embracing the base of the removed particle may be lapped to some extent. In any case such areas will be spaced from each other and be separated by the smooth surface of the chill layer.

As'illustrative of the method herein described, attention is directed to Fig. 4 of the drawings in which the numeral 1th indicates the barrel of the preform prior to its application to the mandrel. The flange is indicated at 11 as extending outwardly adjacent the open end of the barrel. The opposite end of that barrel is formed with a tipped portion 12, the closed end of which is subsequentlyremovedinany desired. manner. In Fig.6

a barrel section has been illustrated after it has been applied in shrinking contact to the mandrel of the Molinari-Magash machine. In both of these views a substantially exaggerated showing has been resorted to in order to illustrate the irregularities of surface and the projecting particles. Thus, the numeral 13 indicates discrete particles of material which may extend into the bore 14 of the barrel. In certain instances it has been found that pockets or reduced surfaces 15 are also present in the bore face. As afore stated, both the relative sizes of these particles and recessed portions have, for the purposes of illustration, been greatly exaggerated. Especially where pockets do exist they will be in effect microscopic both in area and depth.

in Fig. 6 the plunger 16 has been shown as projected into the bore 14- of the barrel. In this view there has also been illustrated a layer of abrasive 17 which provides a film of very minute thickness interposed between the barrel bore and the plunger as these parts are moved with respect to each other. Because of the hard smooth surface of the bore face, the relatively short stroke of movement and the fineness of the abrasive 17, the latter does not affect this surface to the same extent that it acts on and laps the sealing surface of the piston. In Fig. 7 one of the particles 13 has been shown as it is engaged and in process of being severed by the action of the plunger 16. Again in that view the particle has been greatly exaggerated in size for the purpose of illustration as has also the ground and lapped sealing surface of the piston. It will be appreciated that where the particle is not simply severed and subsequently removed by a cleaning and washing operation, such portions of it as ride between the face of the bore 14- and the surface of piunger 16 will be completely reduced to microscopic size fragments which may readily be eliminated without damage to the barrel or plunger surfaces. Thereupon material of this nature will be removed by the subsequent cleaning operations to which the parts are subjected.

In any event, a syringe assembly results which may embrace the physical structures shown in Figs. 1 to 3. In those views the numeral 18 indicates a barrel provided with a flange 19 defining an open or plunger-receiving end. This flange may embody any desired configuration. The opposite end of the barrel is furnished with a bore or passage and a conveniently reduced needle-supporting portion 20 to which a tube section 21 is conveniently afiixed for connection with a hypodermic needle. The exterior face of barrel 18 presents suitably applied indicia 22. The plunger has a bore-entering portion 23 which, as afore brought out, is ground and otherwise finished to furnish a satiny, truly circular surface. An actuating portion 24 forms a part of the plunger and extends beyond the barrel for the purpose of reciprocating the plunger within the same. The diameter of the plunger is substantially constant throughout its entire bore-entering and sealing portion. Therefore, the sealing surface is effective throughout the entire length of this portion.

The transparency of barrel 18 is not affected to any apparent extent by the removal of particles 13. Therefore, insofar as is apparent, the barrel wall is clear and a physician may view the interior of the barrel bore, having no difficulty in determining precisely the extent to which the plunger is projected into the same. Due to the fact that an assembly is involved which embraces a barrel bore incorporating a substantialiy unbroken chill layer with a very smooth exposed surface and a plunger with a finely ground surface, a seal is furnished such that the danger of leakage is reduced to a minimum. This danger is also further reduced due to the overall length of the seal which, as afore brought out, exists throughout the entire sealing zone of the plunger body. This zone is substantial area rather than being limited merely to a zone adjacent the end ofthat plunger. As a consequence of this extended sealing zone or-surface the life of the assembly is increased to a great extent. In other words,

there is not involved merely a very small area of seal which, after limited use, including sterilization, cleaning with detergents, etc., is reduced so that the unit is unsuitable for further use. Also, due to the lapping of the piston, it has imparted to it a finefinish. Such a surface is less susceptible to attack by detergents and other materials. The substantially unbroken bore surface of the barrel is, of course, very resistant to such attacks. Consequently, there are produced assemblies which are more uniform than those as heretofore provided by hand methods.

Thus, among others, the several objects of the invention as specifically aforenoted are achieved. Obviously changes in the structure and in the steps of the method may be resorted to without departing from the spirit of the invention as defined by the claims.

We claim:

1. A method of forming a glass hypodermic syringe barrel which includes providing a glass barrel preform presenting a bore characterized by an integral smooth surface, shrinking said barrel under the action of heat and pressure and as an incident to such shrinking bringing discrete particles of material to extend beyond said bore surface at points casually spaced with respect to each other with major bore areas intervening such particles remaining in smooth unbroken condition and removing said particles from said bore surface.

2. A method of forming a hypodermic syringe barrel which includes providing a barrel preform presenting a bore characterized by an integral smooth surface, shrinking said barrel, under the action of heat and pressure and as an incident to such shrinking bringing discrete particles of material to extend beyond said bore surface at points casually spaced with respect to each other with major bore areas intervening such particles and remaining in smooth, unbroken condition and removing said particles from said bore surface with the line of severance being not beyond such surface to prevent a transparent finished syringe barrel, the clear portion of which is interrupted only by microscopic areas defining points at which particles have been severed.

3. A method of forming a hypodermic syringe barrel which includes providing a barrel preform presenting a bore characterized by an integral smooth surface layer, shrinking said barrel under the action of heat and pressure to thicken said layer and bring discrete particles of material to extend into said bore surface at points casually spaced from each other, major bore areas intervening such particles and remaining in smooth, unbroken condition and in finally removing said particles from said bore surface.

4. A method of forming a glass hypodermic syringe barrel which includes providing a barrel preform presenting a bore characterized by an integral, smooth surface, shrinking said barrel under the action of heat and pressure and as an incident to such shrinking bringing discrete particles of material to extend beyond said bore surface, providing a glass plunger with a ground exterior face, introducing such plunger into said bore with a layer of abrasive interposed between the smooth bore surface and the plunger surface, effecting relative movements between said plunger and barrel to remove the particles from said bore surface and discontinuing such relative movements prior to abrading the bore surface at points between those at which said particles extend inwardly to thereby leave between such points a smooth, unbroken surface.

5. A method of forming a hypodermic syringe barrel which includes providing a glass barrel preform presenting a bore characterized by an integral smooth surface, shrinking said barrel under the action of heat and pressure and as an incident to such shrinking bringing discrete particles of material to extend beyond said bore surface at points casually spaced with respect to each other with major bore areas intervening such particles and remaining in smooth, unbroken condition, removing the inwardly extending portions of said particles and lapping the surfaces of the areas defining the zones of particle removal.

6. A method of forming a glass hypodermic syringe barrel which includes providing a glass barrel preform presenting a bore characterized by an integral smooth surface, shrinking said barrel under the action of heat and pressure and as an incident to such shrinking bringing discrete particles of material to extend beyond said bore surface, providing a plunger having a body and an end portion, treating the body portionof said plunger to present a circular face of uniform, cross sectional area throughout a substantial portion of its entire length, such treating being continued until the diameter of said plunger is substantially equal to the diameter of the barrel bore as defined by the major portion thereof intervening the points at which the particles extend inwardly from its face, introducing the end of said plunger into said barrel, effecting relative movements between said plunger and barrel after such introduction to sever the inwardly projecting particle portions from the surface of said bore and discontinuing such movements prior of abrading the smooth bore surface at points between those at which particle severance occurs.

7. A method of forming a glass hypodermic syringe barrel which includes providing a barrel preform presenting a bore characterized by an integral, clear and uninterrupted smooth surface, shrinking said barrel under the action of heat and pressure and as an incident to such shrinking bringing discrete particles of material to extend beyond said bore surface, discontinuing such shrinking with said bore presenting a substantially truly circular cross section and with smooth bore portions extending throughout the major surface of said bore at points intervening said particles, providing a plunger having a body and an end portion, treating a major area of the body portion of said plunger to present a circular face of uniform cross sectional area throughout its entire length and having a diameter substantially equal to that of the shrunken bore of said barrel as defined by its major surface, introducing the end of said plunger into the barrel bore with a layer of abrasive interposed between the faces of said bore and plunger, effecting relative movements between said plunger and barrel after such introduction to sever the inwardly projecting particle portions from the surface of said bore, reducing the removed particles by said abrasive and discontinuing such relative movements prior to abrading the bore surface at points between those at which particles have theretofore extended inwardly.

8. A method of forming a syringe barrel which comprises shrinking a tube preform consisting essentially of glass including minute particles which are not wholly reduced, said method including the employment of a tubular glass preform of such composition, discontinuing the shrinking of the preform after decreasing its bore diameter to a substantially true circular configuration and as an incident to such shrinkage, bringing discrete composition particles to extend beyond the barrel bore at points casually spaced from each other and with uninterrupted, smooth bore portions of major area intervening such particles and removing said inwardly extending particles from the bore surface so that the latter presents, in its final aspect, a clear smooth transparent face interrupted only by spaced microscopic areas defining the points at which particles extended inwardly prior to their removal from the bore surface.

9. A method of forming a syringe barrel which comprises shrinking a tube preform consisting essentially of glass including minute particles which are not wholly reduced, said method including the employment of a tubular glass preform of such composition, discontinuing the shrinking of the preform after decreasing its bore diameter to a substantially true circular configuration and as an incident to such shrinkage, bringing discrete composition particles to extend beyond the barrel bore at points casually spaced from each other and with uninterrupted, smooth bore portions of major area intervening such particles, employing a plunger of selected diameter to be received in said barrel bore and which diameter corresponds to the bore diameter, introducing the plunger into the bore in the presence of abrasive and effecting movement of the plunger with respect to the bore surface to remove such particles therefrom so that the bore presents major areas of smooth, clear and transparent surface interrupted only by spaced microscopic areas defining the points at which said particles extended inwardly prior to their removal from the bore surface.

References Cited in the file of this patent UNITED STATES PATENTS Reich May 17, McElroy et a1. July 31, Conradson Mar. 2, Poppe Sept. 24, McCormack et al. Apr. 25, Gunther Dec. 13, Clerici Mar. 17, Smith Jan. 1, Shaw Dec. 11,

Kolodny June 9, 

